Obesity is considered a long-term metabolic disease. There are several serious medical sequelae related to obesity. There are over 1 billion overweight individuals worldwide with 100 million clinically obese. The increasing health care costs of treating obesity related diseases in the US alone are estimated at over $100 billion annually. Current methods for treating obesity include behavioral modification, diet, surgery (gastroplasty), administering pharmaceutical agents that block appetite stimulating signals or absorption of nutrients (fat), and administering agents that increase thermogenesis or fat metabolism. Some of these methods have disadvantages in that they rely on patient resolve, are invasive, or have unwanted side effects. An understanding of the mechanisms by which obesity is regulated may provide important therapeutic information.
Obesity is frequently associated with insulin resistance and together constitutes risk factors for later development of type 2 diabetes and cardiovascular diseases. Insulin resistance occurs well before development of type 2 diabetes, and insulin is overproduced to compensate for the insulin resistance and to maintain normal glucose levels. Type 2 diabetes ensues, as the pancreas can no longer produce enough insulin to maintain normal glucose levels. Early stages of type 2 diabetes are associated with elevated levels of insulin but as the disease progresses the pancreas may fail to produce insulin, resulting in increased blood glucose levels. Diabetes is a significant risk factor for both heart disease and stroke and is the leading cause of blindness and end-stage renal failure.
Diabetes is a disorder characterized by hyperglycemia due to deficient insulin action that may result from reduced insulin production or insulin resistance or both. Diabetes mellitus is a polygenic disorder affecting a significant portion of the people in the world. It is divided into two types. In type I diabetes, or insulin-dependent diabetes mellitus (IDDM), patients produce little or no insulin, the hormone that regulates glucose utilization. In type 2 diabetes, or noninsulin-dependent diabetes mellitus (NIDDM), patients often have plasma insulin levels that are the same compared to nondiabetic humans; however, these patients have developed a resistance to the insulin stimulating effect of glucose and lipid metabolism in the main insulin-sensitive tissues, i.e., muscle, liver and adipose tissues, and the plasma insulin levels are insufficient to overcome the pronounced insulin resistance. Additionally, glucotoxicity, which results from long-term hyperglycemia, induces tissue-dependent insulin resistance (Nawano et al., Am. J. Physiol. Endocrinol. Metab., 278, E535-543) exacerbating the disease.
Type 2 diabetes accounts for over 90% of all diabetes cases. It is a metabolic disorder characterized by hyperglycemia leading to secondary complications such as neuropathy, nephropathy, retinopathy, hypertriglyceridemia, obesity, and other cardiovascular diseases generally referred to as metabolic syndrome.
Metabolic syndrome is a combination of medical disorders that increase one's risk for cardiovascular disease and diabetes. The symptoms, including high blood pressure, high triglycerides, decreased HDL and obesity, tend to appear together in some individuals. Metabolic syndrome is known under various other names, such as (metabolic) syndrome X, insulin resistance syndrome or Reaven's syndrome.
Diabetes and obesity (sometimes now collectively referred to as “diabesity”) are interrelated in that obesity is known to exacerbate the pathology of diabetes and greater than 60% of diabetics are obese. Most human obesity is associated with insulin resistance and leptin resistance. In fact, it has been suggested that obesity may have an even greater impact on insulin action than diabetes itself (Sindelka et al., Physiol Res., 51, 85-91). Additionally, several compounds on the market for the treatment of diabetes are known to induce weight gain, a very undesirable side effect to the treatment of this disease. Therefore, a compound that has the potential to treat both diabetes and obesity would provide a significant improvement over current treatments.
The fibroblast growth factor (FGF) family of signaling polypeptides regulates a diverse array of physiologic functions including mitogenesis, wound healing, cell differentiation and angiogenesis, and development. Both normal and malignant cell growth as well as proliferation are affected by changes in local concentration of these extracellular signaling molecules, which act as autocrine as well as paracrine factors. Autocrine FGF signaling may be particularly important in the progression of steroid hormone-dependent cancers and to a hormone independent state (Powers et al., Endocr. Relat. Cancer, 7, 165-197). FGFs and their receptors are expressed at increased levels in several tissues and cell lines and overexpression is believed to contribute to the malignant phenotype. Furthermore, a number of oncogenes are homologues of genes encoding growth factor receptors, and there is a potential for aberrant activation of FGF-dependent signaling in human pancreatic cancer (Ozawa et al., Teratog. Carcinog. Mutagen., 21, 27-44).
Fibroblast growth factors (FGFs) and their receptors (FGFRs) are critical for the development of most cell types. The cellular response to FGFs is transmitted via four types of high affinity transmembrane tyrosine-kinase fibroblast growth factor receptors numbered 1 to 4 (FGFR1 to FGFR4). There are at least 22 distinct FGF ligands and, as indicated above, four receptors (FGFR1-4). Different ligand/receptor pairs regulate cell growth in either a positive or negative manner, depending on the cell type and stage of development (Dailey et al., Cytokine Growth Factor Rev. 16, 233-247; Eswarakumar et al. Cytokine Growth Factor Rev., 16, 139-149) Upon ligand binding, the receptors dimerize and auto- or trans-phosphorylate specific cytoplasmic tyrosine residues to transmit an intracellular signal that ultimately reaches nuclear transcription factor effectors. Mitogenic signaling by these FGFRs is subsequently mediated via a number of pathways, including the ras/raf/MAP kinase cascade (Ozawa et al., Teratog. Carcinog. Mutagen., 21, 27-44).
Alternative splicing of the mRNA for the FGFRs 1, 2, 3 and 4 results in a wide range of receptor isoforms with varying ligand-binding properties and specificities. (Klagsbrun et al., Cell, 67, 229-231; Jaye et al., Biochim Biophys acta, 1135, 185-199). With different receptor possibilities and at least 22 ligands in the FGF family, there is a great deal of diversity in the FGF signaling pathway (Powers et al., Endocr. Relat. Cancer, 7, 165-197). Furthermore, expression and localization of the receptor isoforms is regulated in a tissue specific manner. Thus, the various FGFs may exert different influences upon different cell types by interacting with different receptor splice variants to initiate unique intracellular signaling cascades, leading to a panoply of cellular responses (Ozawa et al., Teratog. Carcinog. Mutagen., 21, 27-44).
Fibroblast growth factor receptor 4 (also known as FGF receptor-4, TKF; tyrosine kinase related to fibroblast growth factor receptor; hydroxyaryl-protein kinase; tyrosylprotein kinase; Fgfr4; FGFR-4; FGFR4; CD334, FGFR4_HUMAN and JTK2) has high affinity for the acidic and/or basic fibroblast growth factors. (Armstrong et al., Genes Chromosomes Cancer, 4, 94-98).
The FGFR4 gene was mapped to 5q35.1-qter, the long (q) arm of chromosome 5 between position 35.1 and the end (terminus) of the arm, an area involved in leukemias and lymphomas. (Armstrong et al., Genes Chromosomes Cancer, 4, 94-98). More precisely, the FGFR4 gene is located from base pair 176,446,526 to base pair 176,457,732 on chromosome 5. The mouse Fgfr4 gene was mapped to mouse chromosome 13 located from base pair 54,235,030 to base pair to 54,251,130, in a region of homology of synteny with distal human 5q. (Avraham et al., Genomics, 21, 656-658).
The FGFR4 gene spans approximately 11.3 kb and is composed of 18 exons ranging in size from 17 to 600 bp. Exon 1 is untranslated and preceded by structural elements characteristic of a TATA-free promoter. Short tandem repeat polymorphisms were identified in introns 2 and 16 of FGFR4. (Kostrzewa et al., Mammalian Genome, 9, 131-135)
Although FGFRs generally have been shown to have wide distribution throughout the body. To date, FGFR4 has only been found in a few tissues. Among a wide variety of cells and tissues tested, including human lymphocytes and macrophages, FGFR4 was found to be expressed in the lung and in some tumors of lung origin as well as in malignancies not derived from lung tissues. (Holtrich et al., Proc. Nat. Acad. Sci., 88, 10411-10415). FGFR4 has also been found to be expressed in the liver and in adipose tissues. (Patel et al., JCEM, 90(2), 1226-1232).
FGFR4 has also been found to be expressed in certain carcinoma cell lines. In the FGFR4 gene transcript from a mammary carcinoma cell line, a G-to-A transition was discovered that resulted in the substitution of glycine by arginine at position 388 in the transmembrane domain of the receptor. The arg388 allele was also found in cell lines derived from a variety of other tumor types as well as in the germline of cancer patients and healthy individuals. Analysis of 3 geographically separated groups indicated that it occurs in approximately 50% of humans. Investigation of the clinical data of 84 breast cancer patients revealed that homo- or heterozygous carriers of the arg388 allele had a significantly reduced disease-free survival time (P=0.01) within a median follow-up of 62 months. Moreover, the FGFR4 arg388 allele was associated with early metastasis and advanced tumor-node metastasis stage in 82 colon cancer patients. Consistent with this finding, the mammary tumor cell line expressing FGFR4 arg388 exhibited increased motility relative to cells expressing the FGFR4 gly388 isotype. The results supported the conclusion that the FGFR4 arg388 allele represents a determinant that is innocuous in healthy individuals but predisposes cancer patients for significantly accelerated disease progression. (Bange et al., Cancer Res., 62, 840-847).
Fibroblast growth factor 1 (FGF1) plays an important role in adipogenesis. (Hutley et al., Diabetes, 53, 3097-3106). Further, FGF1 has been shown to bind FGFR4 which is also expressed in adipose tissue, (Patel et al., JCEM, 90(2), 1226-1232).
Additionally, FGFR4 has been shown to play a role in systemic lipid and glucose homeostasis. FGFR4-deficient mice on a normal diet exhibited features of metabolic syndrome that include increase mass of insulin resistance, in addition to hypercholesterolemia. FGFR4 deficiency was shown to alleviate high-fat diet-induced fatty liver in a certain obese mouse model, which is also a correlate of metabolic syndrome. Restoration of FGFR4, specifically in hepatocytes of FGFR4 deficient mice, decrease plasma lipid level and restored the high fat diet-induced fatty liver but failed to restore glucose tolerance and sensitivity to insulin. (Huang et al., Diabetes, 56, 2501-2510).
Effective treatments are needed for diabetes, obesity, metabolic syndrome and other diseases and conditions thereof. Provided herein is data establishing a role for FGFR4 in both diabetes and obesity. The data supports targeting of FGFR4 for treatment of a range of metabolic conditions, including diabetes, obesity and metabolic syndrome. Therefore, among the objectives herein, it is an object to provide compounds, compositions and methods for the treatment of such diseases and conditions.
Antisense technology is emerging as an effective means for reducing the expression of specific gene products and therefore may prove to be uniquely useful in a number of therapeutic, diagnostic, and research applications for the modulation of FGFR4 expression.
The present invention provides compositions and methods for modulating FGFR4 expression, including modulation of the truncated mutants and alternatively spliced forms of FGFR4.
There remains a need for non-invasive therapies to promote weight loss in obese individuals with improved specificity to avoid side-effects and the present invention meets this need.